Helmets are worn in sports (e.g., hockey, lacrosse, football, etc.) and other activities (e.g., motorcycling, industrial work, military activities, etc.) to protect their wearers against head injuries. To that end, helmets typically comprise a rigid outer shell and inner padding to absorb energy when impacted.
Various types of impacts are possible. For example, a helmet may be subjected to a linear impact in which an impact force is generally oriented to pass through a center of gravity of the wearer's head and imparts a linear acceleration to the wearer's head. A helmet may also be subjected to a rotational impact in which an impact force imparts an angular acceleration to the wearer's head. This can cause serious injuries such as concussions, subdural hemorrhage, or nerve damage. Also, a helmet may experience high-energy impacts (e.g., greater than 40 Joules) and/or low-energy impacts (e.g., 40 Joules or less) that can cause different kinds of harm or injury.
Although helmets typically provide decent protection against linear impacts, their protection against rotational impacts is often deficient. This is clearly problematic given the severity of head injuries caused by rotational impacts.
Also, while various forms of protection against linear impacts have been developed, existing techniques may not always be adequate or optimal in some cases, such as for certain types of impacts (e.g., high- and low-energy impacts).
For these and other reasons, there is a need for improvements directed to providing helmets with enhanced impact protection.